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([38.34.87.7]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2e9a5f52b32sm1730686a91.5.2024.11.07.09.51.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Nov 2024 09:51:18 -0800 (PST) From: Eduard Zingerman To: bpf@vger.kernel.org, ast@kernel.org Cc: andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, kernel-team@fb.com, yonghong.song@linux.dev, memxor@gmail.com, Eduard Zingerman Subject: [RFC bpf-next 06/11] bpf: KERNEL_VALUE register type Date: Thu, 7 Nov 2024 09:50:35 -0800 Message-ID: <20241107175040.1659341-7-eddyz87@gmail.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241107175040.1659341-1-eddyz87@gmail.com> References: <20241107175040.1659341-1-eddyz87@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Follow-up patch adds inlinable kfuncs as subprograms of a bpf program being verified. Bodies of these helpers are considered trusted and don't require verification. To facilitate this, add a new register type: KERNEL_VALUE. - ALU operations on KERNEL_VALUEs return KERNEL_VALUE; - stores with KERNEL_VALUE destination registers are legal; - loads with KERNEL_VALUE source registers are legal and set destination registers to KERNEL_VALUE; - KERNEL_VALUEs do not have any additional associated information: no ids, no range, etc. Signed-off-by: Eduard Zingerman --- include/linux/bpf.h | 1 + kernel/bpf/log.c | 1 + kernel/bpf/verifier.c | 24 +++++++++++++++++++++++- 3 files changed, 25 insertions(+), 1 deletion(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 2bcc9161687b..75f57f791cd3 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -941,6 +941,7 @@ enum bpf_reg_type { PTR_TO_BUF, /* reg points to a read/write buffer */ PTR_TO_FUNC, /* reg points to a bpf program function */ CONST_PTR_TO_DYNPTR, /* reg points to a const struct bpf_dynptr */ + KERNEL_VALUE, /* pointer or scalar, any operation produces another KERNEL_VALUE */ __BPF_REG_TYPE_MAX, /* Extended reg_types. */ diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c index 4a858fdb6476..87ab01b8fc1a 100644 --- a/kernel/bpf/log.c +++ b/kernel/bpf/log.c @@ -463,6 +463,7 @@ const char *reg_type_str(struct bpf_verifier_env *env, enum bpf_reg_type type) [PTR_TO_FUNC] = "func", [PTR_TO_MAP_KEY] = "map_key", [CONST_PTR_TO_DYNPTR] = "dynptr_ptr", + [KERNEL_VALUE] = "kval", }; if (type & PTR_MAYBE_NULL) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d4ea7fd8a967..f38f73cc740b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2388,6 +2388,12 @@ static void mark_reg_unknown(struct bpf_verifier_env *env, __mark_reg_unknown(env, regs + regno); } +static void mark_reg_kernel_value(struct bpf_reg_state *reg) +{ + __mark_reg_unknown_imprecise(reg); + reg->type = KERNEL_VALUE; +} + static int __mark_reg_s32_range(struct bpf_verifier_env *env, struct bpf_reg_state *regs, u32 regno, @@ -4534,6 +4540,9 @@ static bool __is_pointer_value(bool allow_ptr_leaks, if (allow_ptr_leaks) return false; + if (reg->type == KERNEL_VALUE) + return false; + return reg->type != SCALAR_VALUE; } @@ -7208,6 +7217,9 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn } else if (reg->type == PTR_TO_ARENA) { if (t == BPF_READ && value_regno >= 0) mark_reg_unknown(env, regs, value_regno); + } else if (reg->type == KERNEL_VALUE) { + if (t == BPF_READ && value_regno >= 0) + mark_reg_kernel_value(regs + value_regno); } else { verbose(env, "R%d invalid mem access '%s'\n", regno, reg_type_str(env, reg->type)); @@ -14319,6 +14331,13 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env, if (BPF_SRC(insn->code) == BPF_X) { src_reg = ®s[insn->src_reg]; + + if (src_reg->type == KERNEL_VALUE || dst_reg->type == KERNEL_VALUE) { + mark_reg_kernel_value(src_reg); + mark_reg_kernel_value(dst_reg); + return 0; + } + if (src_reg->type != SCALAR_VALUE) { if (dst_reg->type != SCALAR_VALUE) { /* Combining two pointers by any ALU op yields @@ -14358,6 +14377,9 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env, return err; } } else { + if (dst_reg->type == KERNEL_VALUE) + return 0; + /* Pretend the src is a reg with a known value, since we only * need to be able to read from this state. */ @@ -15976,7 +15998,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char } if (is_subprog && !frame->in_exception_callback_fn) { - if (reg->type != SCALAR_VALUE) { + if (reg->type != SCALAR_VALUE && reg->type != KERNEL_VALUE) { verbose(env, "At subprogram exit the register R%d is not a scalar value (%s)\n", regno, reg_type_str(env, reg->type)); return -EINVAL; -- 2.47.0